Centrifugal machine



Feb. 18, 1969 H, HILLEBRAND CENTRIFUGAL .MACHINE Filed April 4. 1.967

United States Patent O 3,428,182 CENTRIFUGAL MACHINE Henrich Hillebrand, Braunschweig, Germany, assignor to Braunschweigische Maschinenbauanstalt, Braunschweig, Germany Filed Apr. 4, 1967, Ser. No. 628,316 Claims priority, appliition Germany, Apr. 7, 1966,

U.s. ci. 21o- 369 7 Claims Inf. cl. Bold 33/02 ABSTRACT OF THE DISCLOSURE A centrifugal machine with a rotating frusto-conical basket overlaid by a screen has inside the basket a distributor disc enclosed by an accelerator cone which both This invention relates generally to continuous centrifugal separators, particularly of the kind employed in the sugar industry.

In some such continuous centrifugals, a basket of up- Wardly flaring frusto-conical form whose inner surface is constituted by a perforated screen, is rotated on its vertical axis; the hub of the basket extends inwardly into the basket and may be provided with a charge disc and an accelerating cone flaring towards the bottom of the basket.

It is known to distribute the mixture of liquid and solids to be separated as evenly as possible over the periphery of the screen and to introduce said mixture approximately at the speed of rotation of the screen obtaining in the feed zone, so as to avoid unbalances. Particularly in the processing of highly viscous stock materials, considerable diiculties are experienced which have been responsible for the provision of special distributing and accelerating means from which the material is applied to the separating screen of the centrifugal. There have been proposed charge discs with central feed of the material or accelerating cones which have the large `diameter end lowermost. Also both said elements have been used in combination (e.g. German Utility Model No. 1,778,979 and German Auslegeschrift 1,194,782).

In said centrifugals, a flat charging disc is secured in peripherally spaced relationship to the accelerating cone, eg., by providing intermediate stays, or directly to the hub of the centrifugal. The stock mixture is centrally supplied to the charging disc and, after having been distributed thereon, passes onto the inner wall of the accelerator cone where it travels in the direction of the bottom of the basket, under simultaneous acceleration to the respective peripheral speed of the cone envelope, and is centrifuged over the lower rim of the cone onto the periphery of the separator screen.

In such application of distributing plate and accelerator cone, it was not possible to ensure a homogeneous distribution of the stock material on the periphery of the screen, particularly with highly viscous materials such as massecuite for which continuous centrifugals are frequently used. In highly viscous masses, the jet of the material is easily interrupted, and lengths of the material are deposited on the plate and pass from there without noticeable peripheral acceleration to the inner wall of the accelerator cone where, again without being entrained,

Patented Feb. 18, 1969 they glide to the bottom of the centrifuge; from there they pass finally onto the screen. If subsequently, in the bottom zone of the basket, said pieces are taken up by the screen, there is not only the risk of screen destruction and increased grain breakage but said pieces accumulate on the screen periphery producing unbalances. Experience has shown that centrifugals rotating at high speeds have a strong tendency to develop unbalances, which result frequently in shut downs.

It is, therefore, a principal object of this invention to prevent the drawbacks of an uneven passage even of highly viscous stock material to the screen of the centrifugal basket.

It is another object of the invention to provide a centrifugal separator of the character described in which the stock material can be charged as a layer of homogeneous thickness to the screen in the bottom zone of the basket at a circumferential speed which approximately corresponds to the circumferential speed of the screen in the charging zone.

Other objects and advantages will become apparent from a consideration of the specification and claims.

In accordance with the invention, the charge disc is recessed, preferably semispherically or in form of a calotte, and the wall of the accelerator cone has, at the level of the rim of the disc, an angle of divergence from the vertical which is greater than that of the remaining cone envelope.

By designing the charge disc in form of a trough, which receives the massecuite, the disc contains at all times a certain amount of the stock material which is spun off, depending on the amount of the subsequently received material, over the upper rim of the disc. Therefore, even if the jet of the material is disrupted, lengths thereof are retained on the disc and are entrained by the contact with the material present thereon. As they need some time to reach the upper rim of the disc, they can be distributed over the whole circumference of the disc and cannot glide off without being sufficiently accelerated as it happened with at discs.

'The specific design of the surface of the accelerator cone at the level of the disc continues the distributing effect started on the disc. After being projected on the cone in the area of the greatest angle of divergence from the vertical, the material is forced vigorously towards the outside and is temporarily backed up on transition to the cone surface of lesser inclination. This temporary back-up produces a uniform distribution of the stock material. In this way, the material passes as a layer of even thickness onto the adjoining zone of the cone surface and travels thereon towards the bottom of the basket where, due to said uniform thickness, it is spun off uniformly onto the periphery of the screen of the basket.

It is of advantage to construct the frusto-conical basket in the area of the lower rim of the accelerator cone with an inner Wall which has a lesser inclination than the remaining wall of the centrifugal; in this way, the same phenomena which took place at the transfer of the massecuite from the distributor disc to the accelerator cone, are essentially repeated in the zone where the material is transferred to the basket. As a result, the supply of the material is further homogenized if, in spite of the means described, the material should not yet .have been present as a layer of homogeneous thickness on the inner Wall of the accelerator cone. The described transfer of the material from the accelerator cone to the screen compensates also any interference which might be produced by connecting stays between cone yand hub or cone and charge disc. When such connecting stays are used to support the accelerator cone, it is of advantage to arrange the same in the upper third of the cone so as to reduce their disturbing effects and to allow the material to reform a uniform layer in the area below the stays when it glides down along the inner wall of the accelerator cone.

The less inclined zones of the accelerator cone at the level of the charge disc and the corresponding zones of the basket at the lower rim of the accelerator cone produce a particularly favorable distributor effect when said zones form angles up to 45 with the'horizontal plane.

In order to obtain a thorough uniform distribution of the stock material already on the charge disc, the invention provides further for a feed funnel centrally disposed above said disc so as to feed the charge independently of the position of the stock inlet or feed conduit into the troughshaped recess in the center of the disc.

The annular slots formed at the transfer points between the rim of the disc and the accelerator cone, and between the accelerator cone and the less inclined zone of the basket, should be kept as small as possible to ensure approximately tangential impact of the material on the respective impinged surfaces of the cone or centrifugal.

The invention will be better understood by reference to the 4accompanying drawing, in which a preferred embodiment is illustrated by way of example, and which is a diagrammatic vertical sectional view of a continuous centrifugal having a distributor disc and an accelerator cone in accordance with the invention.

The centrifugal illustrated in the drawing includes the frusto-conical basket 1 having its large diameter end at the top. The basket has a hub 2 which is secured on shaft 3. Said shaft 3 and hub 2 project into the basket 1. On the hub 2, there is secured the charge disc 4 which has a trough-like recess 5.

The hub 2 and the feed disc 4 are enclosed by an accelerator cone 6 which, at the level of the rim 7 of the disc, has a zone of lesser inclination 8, i.e. an area of the envelope whose angle of divergence from the vertical is greater than the angle of the remaining envelope.

The accelerator cone 6 is supported by stays 17 connected to the disc 4, whereby said stays are relatively thin and arranged in the upper third of the cone.

The accelerator cone 6 is provided with an upper central aperture 9 through which the material is charged onto the disc 4 into the trough-like recess 5 thereof. A feed funnel 10 disposed below the admission conduit 11 directs the material into the trough of the disc 4. The feed funnel is connected by any suitable support means to a stationary member of the centrifugal, e.g. to its housing. The inlet conduit 11 can, if desired, be sunk into the funnel 10.

The basket 1 is enclosed by a housing 12 which has a base plate 13 receiving the shaft 3.

The accelerator cone 6 extends over the hub 2 downwardly to the bottom 14 of the basket 1. At the level of the lower rim 15 of the cone 6, said bottom 14 is provided with an inner wall 16 which has a lesser inclination than the remaining walls of the frusto-conical centrifugal As will be seen on viewing the drawing, the angles between the horizontal plane and the fiat-conical area 8 of the accelerator cone 6 as well as between the horizontal plane and the area 16 of the bottom 14 of the centrifugal, are both less than 45 The feed funnel 10 ensures the stock material to be charged into the center of the trough 5 of the distributor disc 4 where, due to the rotary motion of the disc 4 rotating with the centrifugal, the material, while being entrained in the direction of rotation, travels upwardly and passes over the upper rim 7 of the disc onto the area 8 of lesser inclination of the accelerator cone. From there, the material travels along the inner wall of the accelerator cone to its lower rim 15 and is transferred to the conical zone 14 of small inclination of the bottom 14 of the basket. The trough-shaped design of the disc 4 as well as the conical areas 8 and 14 of relatively small inclination of the accelerator cone 6 and the basket bottom 14, respectively, provide for an improved homogeneous distribution of the charged material on the periphery of the accelerator cone and on the screen of the basket 1.

Thereby, the slots between the upper rim 7 of the disc 4 and the zone 8, and between the lower rim 15 of the cone 6 and the zone 16 of basket bottom 14 are kept relatively narrow. Said narrow slots, in coaction with the respective conical areas of relatively small inclination, ensure an approximately tangential impact of the massecuite at a peripheral speed which corresponds approximately to the peripheral speed of the respective point of impact.

I claim:

1. In a centifugal machine of the character wherein a generally frusto-conical basket means having an upwardly and outwardly flaring discharge end and a perforated screen surface is mounted on a shaft for rotation about a vertical axis, said basket being provided with a central hub means projecting upwardly into the basket, distributing disc means and accelerating cone means concentrically supported on said hub means within the basket means, said distributing disc means being provided with a generally hemispherically shaped dnwnwardly extending concentrically arranged recess for receiving material to be centrifuged, said accelerating cone means having a downwardly and outwardly flaring discharge end and being provided with a central opening at its upper end to permit downward flow of material into said recess in the distributing disc means, the inner surface of the accelerating cone means being divided by a medial horizontal plane into upper and lower portions; the angle of flare with respect to said horizontal plane of said upper portion being substantially less than the angle of flare of the lower portion, whereby material received on said upper portion from the distributing disc means is temporarily backed-up at the transition area between said upper and lower portions to produce a uniform distribution of material.

2. A centrifugal machine as claimed in claim 1 comprising thin supporting stay means connecting the upper third of said accelerator means with said hub.

3. A centrifugal machine as claimed in claim 1 comprising thin supporting stay means connecting the upper third of said accelerator means with said disc means.

4. A centrifugal machine as claimed in claim 1 comprising a feed funnel arranged centrally above the recess of said disc means.

5. A centrifugal machine as claimed in claim 1 wherein the smaller angle of are is less than 45 6. A centrifugal machine as claimed in claim 1 wherein the inner wall of the frusto-conical basket in the area im pinged by the material fed from the accelerator means has an inclination towards the horizontal plane which is smaller than the inclination of the other conical portions of the wall.

7. A centrifugal machine as claimed in claim 6 wherein the smaller angle of flare is less than 45 References Cited UNITED STATES PATENTS 2,343,327 3/1944 Reynolds 210-369 X 2,883,054 4/1959 Sanchez 210-369 X 3,226,257 12/ 1965 Steele et al 210-369 X 3,276,591 10/1966 Hultsch 210--377 X 3,302,794 2/ 1967 Laven 210-369 SAMIH N. ZAHARNA, Primary Examiner.

J. L. DE CESARE, Assistant Examiner.

U.S. Cl. X.R. 

